Wet Film Research Articles

Ultrasonic spray coating as an approach for large-area polymer OLEDs: The influence of thin film processing and surface roughness on electrical performance

In this article we present a detailed comparison of ultrasonic spray coating and spin coating for the fabrication of polymer organic light-emitting diodes (OLEDs). Single-carrier devices of hole-transporting polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4’(N-(4-sec-butylphenyl))) diphenylamine] (TFB) were fabricated by ultrasonic spray coating. Uniform reference devices using spin coating were also made. We have shown, across a range of device thicknesses from 37 nm to 138 nm, typical of those used in OLED hole-transport layers, that there is no statistical difference in the hole-injection efficiency between ultrasonic spray coating and spin coating. We have also demonstrated the importance of controlling the roughness of the films and we determine a threshold of 10 nm average roughness below which injection efficiency is not controlled by roughness. However, above 10 nm roughness we find a reduction in injection efficiency up to an 86 % loss in performance for roughnesses of the order of 40 % the thickness of the film. By optimising the deposition parameters, in order to allow the wet films to start to equilibrate, we find a wide processing window for smooth uniform films with excellent injection efficiency. This work reinforces the importance of ultrasonic spray coating as a potential route to high volume manufacturing of OLED based technology.

Prevalence of bacterial vaginosis among antenatal attendees with abnormal vaginal discharge in a secondary health facility in Delta State, Nigeria

Introduction: Bacterial vaginosis (BV) is the most common lower genital tract syndrome among women of reproductive age with significant adverse outcome in pregnancy. Routine screening of antenatal patients for BV is not recommended, however, it is important to determine its prevalence especially in pregnant women who complain of abnormal vaginal discharge. Methods: This was a cross-sectional study of 340 antenatal attendees who complained of an abnormal vaginal discharge. The high vaginal swab was collected from each woman and subjected to wet film and Gram reaction. The diagnosis of BV was made using the Amsel's clinical criteria. Data were analyzed using the EPI-INFO statistical package and the results were presented as percentages and proportions. Results: BV was detected in 105 pregnant women with abnormal vaginal discharge, therefore, giving a prevalence rate of 30.4%. Positive correlates of BV included multiple sexual partners (P = 0.0001) and cigarette smoking (P = 0.008). Conclusion: BV is a prevalent disorder in pregnant women with abnormal vaginal discharge.

A Survey of Trypanosome Species Circulating In Pigs In Three Selected Local Government District of Enugu State, Nigeria

A cross sectional survey of trypanosomosis of pigs was carried out in three randomly selected Local Government Areas (Nsukka, Udenu and Igbo Eze South) out of the six local government areas in Enugu North Senatorial Zone. Blood samples were randomly collected from a total of 1800 pigs from abattoirs and farms and were examined for trypanosomes parasites using standard parasitological methods: wet film, buffy coat and Giemsa-stained thin smear preparations. A total of 93 (5.2%) pigs were positive overall. Among the positive samples, Trypanosoma brucei was the predominant species (86.0%), followed by T. congolense (13.9%). The different relative isolation rate for Nsukka, Igbo-Eze South and Udenu Local government areas were 14 (4.7%), 14 (4.7%), and 19 (4.0%) respectively in the dry season, and 17 (5.7%), 17 (5.7%) and 12 (6.3%) in the rainy season respectively. The trypanosome prevalence in males from Nsukka, Igbo-Eze South and Udenu local governments were 6.5%, 6.2% and 4.2% respectively, while report in female were 3.8%, 4.1% and 5.9% in the three local governments respectively. There was no significant variations (p<0.05) with seasons, sex and age groups. It was therefore concluded that porcine trypanosomosis is still endemic in Enugu North Senatorial Zone with T. brucei being the most incriminated as the cause of the disease in the zone.

Fabrication of perovskite solar cells based on vacuum-assisted linear meniscus printing of MAPbI3

Scale-up deposition methods in perovskite solar cell research, are mostly used under humidity environment outside the glove-box. Also, the as-printed absorbing layer before the post-annealing process is always wet. Thus, controlling the morphology and crystallization of perovskite thin-films in up-scaled deposition systems is difficult and strongly investigated by the researchers. In this work, we introduce an anti-solvent-free meniscus printing method in which, the absorbing perovskite film with optimal performance is achieved. To this end, we check the printing parameters to get to the optimized film characteristics. Also, a vacuum chamber (<100 Pa) is used for 30 s to remove the solvent with appropriate pace from the as-printed wet perovskite films. Based on using vacuum process, instead of low surface coverage needle-like morphology, a pinhole-free dense film with appropriate grain-size (400–500 nm) and thickness (~480 nm) was obtained. The perovskite devices with optimized meniscus printed films with and without vacuum process show a PCE of 10.1% and 2.3% respectively (with active area of 0.1 cm2). Also, the conversion efficiency of 8.0% was achieved with an active area of 1 cm2. The result demonstrated the merit of using vacuum process before post-annealing step.

High-Efficiency Spray-Coated Perovskite Solar Cells Utilizing Vacuum-Assisted Solution Processing.

We use ultrasonic spray-coating to fabricate cesium-containing triple-cation perovskite solar cells with a power-conversion efficiency of up to 17.8%. Our fabrication route involves a brief exposure of the partially wet spray-cast films to a low vacuum, a process that is used to control film crystallization. We show that films that are not vacuum-exposed are relatively rough and inhomogeneous, while vacuum-exposed films are smooth and consist of small and densely packed perovskite crystals. The process techniques developed here represent a step toward a scalable and industrially compatible manufacturing process capable of creating stable and high-performance perovskite solar cells.

Akermanite-based coatings grown by pulsed laser deposition for metallic implants employed in orthopaedics

The aim of the present paper is to develop ceramic thin films by laser ablation in order to improve the biological behaviour of metallic implants dedicated to hard tissue restoration. The composition of the coatings was selected within SiO2–P2O5–CaO–MgO–ZnO–CaF2 system, while their processing has gone through two stages: target preparation via a wet chemistry approach and films deposition through a physical deposition method, on titanium substrates. The characteristics of the final layered structures were evaluated by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy and selected area electron diffraction. In vitro investigation techniques were employed for the bioactivity and biocompatibility assessment. The results indicated the growth of nanostructured akermanite-based thin films with an excellent bioactivity and a good effect on stem-type cells, which validates the suitability of such structures for medical implant applications.

Lithography-Based Ceramic Manufacturing (LCM) for Dental Applications

Dental applications like crowns, veneers or bridges require high accuracy to be fitted on the patient’s stump. Stereolithography is an additive manufacturing method, which offers high precision by using light exposure as the layer generating mechanism. In the LCM process, this precision is combined with a thermal post-processing step to achieve full ceramic restorations. The overall production of such ceramic parts in a reproducible way is a highly complex procedure. The first requirement is to find a slurry formulation, which is stable against sedimentation and segregation, that is also processable in a stereolithographic system. Such a formulation has been found by us, which could be shown by rheology measurements. During experiments with this formulation, it could be observed that there is a correlation between wet film thickness and resolution. Several adjustments to the machine have been made, to fully control this parameter. Namely, changes to the vat, the doctor blade and the building platform have been made. The improvement of the process and the quality of the final parts are validated by fabricating Siemens stars and by biaxial bending tests.

Luminescent Intermediates and Humidity-Dependent Room-Temperature Conversion of the MAPbI3 Perovskite Precursor.

Preparation of metal-halide perovskites under room temperature attracts attention because of energy saving by removing thermal annealing. Room-temperature transformation of spin-cast wet films consisting of methylammonium (MA) iodide, PbI2, and dimethylformamide toward solid MAPbI3 perovskite proceeds via several intermediate crystalline states and is strongly dependent on ambient humidity. Light transmission and photoluminescence (PL) microscopy and spectroscopy were used to monitor the growth of crystals and transformation of their properties in time under nitrogen atmosphere at room temperature. Under low humidity, a highly luminescent intermediate phase with low absorption in the visible range appears, with the PL spectra composed of several bands in the range from 600 to 760 nm. We assign these bands to low-dimensional (nanocrystals and two-dimensional inclusions) MAPbI3 intermediates, where the exciton confinement shifts the spectrum to higher energies in comparison with the bulk MAPbI3. The intermediate levels of ambient humidity (10–50%) appear to catalyze the conversion of the intermediate phase to MAPbI3. At a high ambient humidity (>80%), the initially formed MAPbI3 is quickly transformed to the transparent hydrate phase of MAPbI3. The role of ambient water catalyzing the material transformation by competing for Pb coordination with the solvent molecules is discussed.

Preparation of novel organo-montmorillonite and its influence on the acid resistance of hybrid cathodic electrodeposition polyurethane coating

Based on the super-composite effect of clay minerals consisting of silicate layers on the polymer, nano-hybrid organic–inorganic composites have attracted great interest. In this paper, a novel organoclay with reactive hydroxyl group was prepared by incorporation into a hydroxyl-terminated cationic polyurethane oligomer (HTCPU) via interlamination. Sodium montmorillonite was organically modified with HTCPU oligomers in the water medium. The modified organo-montmorillonite was characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction, and thermogravimetric analysis. After sequential poly-addition reactions, the hydroxyl-terminated polyurethane hybrid resins with nano-silica layers were prepared and then the resin mixed with blocked hexamethylene diisocyanate trimer (crosslinking agent) in advance and then was emulsified with deionized water to produce the nano-hybrid electrophoresis coating. A series of PU films were prepared by the electrophoresis process. The optimized baking temperature was determined by in situ FTIR, and the effect of the organo-montmorillonite content on the acid resistance of film was studied. When the mass fraction of organo-montmorillonite was about 0.35%, the PU film showed the best acid resistance. It was found that the desirable appearance and properties could be obtained by a prebake of a temperature of 80°C to remove water in the wet film to avoid the pinholes in the paint film for 20 min, followed by a baking temperature of 135°C for 60 min.

Experimental Investigation of the Tractive Performance of Pneumatic Tires on Ice

ABSTRACTThis investigation was motivated by the need for performance improvement of pneumatic tires in icy conditions. Under normal operation, the pneumatic tire is the only force-transmitting component between the terrain and the vehicle. Therefore, it is critical to grasp the understanding of the contact mechanics at the contact patch under various surfaces and operating conditions. This article aims to enhance the understanding of the tire-ice contact interaction through experimental studies of pneumatic tires traversing over smooth ice. An experimental design has been formulated that provides insight into the effect of operational parameters, specifically general tire tread type, slip ratio, normal load, inflation pressure, ice surface temperature, and traction performance. The temperature distribution in the contact patch is recorded using a novel method based on thermocouples embedded in the contact patch. The drawbar pull is also measured at different conditions of normal load, inflation pressure, and ice temperatures. The measurements were conducted using the Terramechanics Rig at the Advanced Vehicle Dynamics Laboratory. This indoor single-wheel equipment allows repeatable testing under well-controlled conditions. The data measured indicates that, with the appropriate tread design, the wheel is able to provide a higher drawbar pull on smooth ice. With an increase in ice surface temperature, a wet film is observed, which ultimately leads to a significant decrease in traction performance.

Improved Intrapixel Thickness Uniformity of Slot-Coated PEDOT:PSS Films for OLEDs via Dilution and Predrying Treatments

Due to capillary force, solution coating of pristine poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) solution in the presence of banks exhibits poor intrapixel thickness uniformity, shrinking the emission area of organic light-emitting diodes (OLEDs) within pixels. To enhance it, we have applied the predrying treatments (predrying under atmospheric pressure, by heat conduction, and under vacuum) to wet films. However, its impact is minimal because the evaporation rate of wet films is not well-matched to the capillary flow rate of solute during the predrying process. It is tackled by diluting the pristine PEDOT:PSS solution with deionized water such that the evaporation of wet films is retarded and in turn, the convective flow of solute occurs from the pixel edge to the center. With increasing dilution, a noticeable enhancement in its intrapixel thickness uniformity is observed without any sacrifice on the surface morphology. It is found that the predrying effect by heat conduction is more pronounced than that under vacuum. Furthermore, we have demonstrated that slot-die coating rather than spin coating is preferable in the coating of diluted PEDOT:PSS solutions. With the diluted solution and predrying by heat conduction, the thickness uniformity can be enhanced by a factor of 2 and the emission area of OLEDs within pixels is broadened to a great extent.

LOW-TEMPERATURE GROWTH AND ELECTRIC PROPERTIES OF K0.5Na0.5Nbo3 THIN FILMS BY MICROWAVE IRRADIATION

K0.5Na0.5Nbo3 wet films were spin-coated on Pt/Ti/SiO2/Si substrates by chemical solution deposition method. The microwave irradiation was introduced as the annealing method. The microstructure and electric properties of KNN thin films were tested and analyzed. It was found that the KNN thin film can be well crystallized by microwave irradiation at the temperature as low as 425∘C. The KNN thin film annealed at 425∘C gains the uniform microstructure, grain refinement, better electric properties and low leakage current density.

Tailoring Characteristics of PEDOT:PSS Coated on Glass and Plastics by Ultrasonic Substrate Vibration Post Treatment

In this work, we excited as-spun wet films of PEDOT:PSS by ultrasonic vibration with varying frequency and power. This is a low-cost and facile technique for tailoring the structural and surface characteristics of solution-processed thin films and coatings. We deposited the coatings on both rigid and flexible substrates and performed various characterization techniques, such as atomic force microscopy (AFM), scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), transmittance, electrical conductivity, and contact angle measurements, to understand how the ultrasonic vibration affects the coating properties. We found that as a result of ultrasonic vibration, PEDOT:PSS sheet conductivity increases up to five-fold, contact angle of water on PEDOT:PSS increases up to three-fold, and PEDOT:PSS roughness on glass substrates substantially decreases. Our results affirm that ultrasonic vibration can favor phase separation of PEDOT and PSS and rearrangement of PEDOT-rich charge transferring grains. In addition to providing a systematic study on the effect of ultrasonic frequency and power on the film properties, this work also proves that the ultrasonic vibration is a novel method to manipulate and tailor a wide range of properties of solution-processed thin films, such as compactness, chain length and arrangement of polymer molecules, conductivity, and surface wettability. This ultrasonication method can serve organic, printed and flexible electronics.

Application of a chromatic confocal measurement system as new approach for in-line wet film thickness determination in continuous oral film manufacturing processes

The key parameter of the oral film production process is the wet film thickness since it regulates the active pharmaceutical ingredient (API) content of the finished product. There is no general recommendation on how to adjust the gap height of the coating knife during the film manufacturing process to obtain the target content. Therefore, trial and error approaches are common to determine the surplus of drug for every newly developed formulation. This wastes resources, money and time and calls for an adequate in-line tool for wet film thickness measurement during the film manufacturing process to ensure consistent quality. In this work, a chromatic confocal optical probe was implemented into a continuous oral film manufacturing process on a pilot-scale coating bench. The optical probe allows a non-destructive and contactless wet film thickness measurement. The validation of the method showed good results. Linearity was demonstrated over a wide range of film thicknesses (R2 = 0.999). A good precision between different films was revealed by a coefficient of variation smaller than 2%. The robustness investigations showed that the method is applicable for transparent and non-transparent film forming masses. Furthermore, coloring agents, particles in the polymer mass and different viscosities do not influence the thickness measurement.

Luminescent and Transparent Nanocellulose Films Containing Europium Carboxylate Groups as Flexible Dielectric Materials

Transparent, flexible, and luminescent 2,2,6,6-tetramethylpiperidine-1-oxyl radical-oxidized cellulose nanofibril films with europium carboxylate groups (TOCN-Eu) are proposed as potential flexible dielectric materials. The TOCN-Eu films were prepared from TOCN films with sodium carboxylate groups (TOCN-Na) by immersion in Eu(NO3)3 solution and subsequent washing with water and drying of the wet TOCN-Eu hydrogel films. The nanolayered TOCN-Eu films emit red light under ultraviolet-light irradiation and exhibit greatly improved dry and wet mechanical properties, water resistance, thermal stability, oxygen-barrier properties, dielectric breakdown strength, and energy density than conventional TOCN-Na films. These characteristic properties of the TOCN-Eu films are most likely caused by the formation of strong ionic bonds between the carboxylate groups and Eu3+ ions. These high-performance cellulose nanofibril films are promising for application as multifunctional materials in light-emitting, photovoltaic, an...

Evaluation of Diff Quik Staining Method for Detection of Mono Sodium Urate Crystals in Synovial Fluid Using Light and Polarizing Microscopy: A Cross-Sectional Study

Gout is one of the oldest diseases of the medical history that results from the deposition of monosodium urate crystals in joint structures and in periarticular sites in the form of tophi. The evaluation of synovial fluid is integral for the diagnosis of gout and other arthritis of microcrystals. The objective of this cross-sectional study was to evaluate the analysis of synovial fluid by polarizing and light microscopy using wet film and Diff Quik stained films and evaluating usefulness of Diff Quik stain in identifying monosodium urate (MSU) crystals on permanent mounted slides. It was conducted on 100 clinically suspected gout patients in the Department of Clinical Pathology, Bangabandhu Sheikh Mujib Medical University, Dhaka from May 2008 to April 2009. Polarizing Microscopy detected the presence of MSU crystals in 35.71% cases from wet films and 36.73% cases from Diff Quik stained films. Light Microscopy detected crystals in 28 (28.57%) cases from Diff Quik stained samples and in 31.63% cases from wet film samples. Considering wet film polarizing microscopy as gold standard, the sensitivity and specificity of wet film light microscopy was 88.6% and 100.0% respectively, whereas sensitivity and specificity were 80.0% and 100.0% respectively in Diff Quik light microscopy.In Diff Quik polarizing microscopy, sensitivity and specificity were100.0% and 98.4% respectively. The sensitivity and specificity was highest in Diff Quik stained films examined by polarizing microscopy&#x0D; Bangladesh J Med Microbiol 2018; 12 (2): 10-13

Improving the appearance of 3-coat-1-bake multilayer films on automotive bodies

3-coat-1-bake is a coating process which primer-surfacer, basecoat, and clearcoat sprayed on an e-coat substrate by a wet-on-wet technique. However the appearance of the 3-coat-1-bake films has been inferior to that of the conventional 2-coat-1-bake films. Therefore, 3-coat-1-bake coating process has been introduced to only economy-class automobiles. In this study, the surface unevenness is discussed as a quantitative parameter of appearance. We assumed that the surface unevenness of the 3-coat-1-bake films is mainly occurred by not only telegraphing of substrate unevenness but also telegraphing of interface unevenness between coating layers. In this paper, we verify this assumption by focusing on telegraphing of interface unevenness between coating layers and examine to reduce the surface unevenness. To reduce the surface unevenness, it is effective to decrease shrinkage of wet film and/or to minimize interface unevenness between coating layers. The surface unevenness reduced when selecting an isocyanate hardener to the basecoat instead of a melamine resin. Because selecting an isocyanate hardener decreased shrinkage of the basecoat film after loss of the macroscopic flow of the clearcoat film. The surface unevenness greatly reduced in the case of basecoat with a low Tg (glass transition temperature) acrylic resin. A low Tg acrylic resin in the basecoat promotes levelling better. Therefore, this minimized interface unevenness between the basecoat and the clearcoat layers at loss of the macroscopic flow of the clearcoat film. It is verified that to decrease shrinkage of wet film, it is effective to select isocyanate hardener. It is also verified that to minimize interface unevenness between coating layers it is effective to use acrylic resin with low Tg.

Sodium caseinate-magnesium aluminum silicate nanocomposite films for modified-release tablets

The aim of this study was to investigate the effect of clay, magnesium aluminum silicate (MAS), on the properties of sodium caseinate (SC) dispersions and films. Moreover, the SC-MAS dispersions were evaluated for film coating of modified-release tablets. The results showed that MAS addition led to particle flocculation and viscosity synergism in the SC-MAS dispersions. Exfoliated or intercalated nanocomposites of the SC-MAS films could be formed because of the molecular interaction of both components via hydrogen bonding. The puncture strength and elongation of the dry SC films decreased with increasing MAS ratios. However, MAS added enhanced the puncture strength of the wet films and reduced drug permeability and diffusivity across the films in acidic medium because of lower water uptake and denser matrix structure of the films. The SC-MAS dispersions showed strong potential for use as a film coating material with few defects in the coated acetaminophen (ACT) tablets. The ACT release of the coated tablets in acidic medium was modified by varying the MAS ratios and film coating levels. In addition, the SC-MAS coated tablets possessed sustained-release behavior for the drug under simulated gastrointestinal conditions. This finding indicates that the SC-MAS nanocomposite films can be applied as a tablet coating material to modify drug release.

Parasitological and Molecular Detection of Canine Trypanosomiasis From Riyadh Province, Saudi Arabia.

Trypanosoma evansi is the most widespread of the pathogenic salivarian trypanosomes; it causes a serious disease called surra that affects domestic animals such as camels, horses, and dogs, and often leads to reduced productivity and economic losses. Therefore, the objectives of the present study were to determine the prevalence rates of trypanosomiasis using 3 parasitological tests (wet blood film, Giemsa staining, and microhematocrit centrifugation technique) and polymerase chain reaction (PCR) among stray dogs from Riyadh Province, Saudi Arabia. In the current study, 117 dog blood samples collected from certain districts of Riyadh Province showed that 5 of 117 dogs (4.3%) were positive for the genus Trypanosoma. In addition, the findings indicated no effect of dog gender or age on parasite infection. For a more specific diagnosis, PCR amplification of the RoTat 1.2 VSG gene in 5 internal transcribed spacer1-positive samples diagnosed with Trypanosoma indicated that 2 were positive for RoTat 1.2 T. evansi. The absence of the RoTat 1.2 VSG gene in 3 of the 5 T. evansi-positive samples could be explained by the circulation of T. evansi type B in dogs from Saudi Arabia. Thus, this is the first study demonstrating T. evansi type B outside of Africa.

Ag-coated submicron particles of polystyrene formed by dewetting process and their application in multi-functional biosensor-chips

The formation of submicron polystyrene (PS) particles based on dewetting process during spin-coating was investigated. The surface morphologies on glass substrates were analyzed. The formation of particles was achieved using PS with relatively high molecular weight (Mw ≥ 3250). In addition, it was observed that the particle formation proceeded through sequential morphological changes in the order of initial wet thin film, secondary spinodal-decomposed structures, and eventual dewetted particles. One of the fabricated samples exhibited obvious optical resonance in the visible region based on the relationship between particle dimeters and optical wavelengths in the visible region. The optical resonance strongly depended on the ambient refractive index, which can be used for optical sensor-chips. Finally, a multi-functional biosensor-chip was demonstrated to detect glucose in water solutions.